Liquid fuel injection pump for internal combustion engines



July 4, 1933. R. w. VIGERS ET AL 1,917,169

LIQUID FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES Filed Aug.15, 1931 m AH'nys.

llll

Patented July 4, 1933 UNITED STATES PATENT OFFICE ENGLAND, ASSIGNORS TOD. NAPIER & SON

@OMPY OF GREAT BRITAIN LIMITED, O]? LONDON, ENGLAND, A

- nreum FUEL INJEGTION PUHD? FOR INTERNAL COMBUSTION ENGINES Applicationfiled August 13, 1931, Serial No. 556,928, and in Great BritainSeptember 26, 1930.

This invention relates to liquid fuel injection pumps for internalcombustion engines and has for its object to provide an improved fuelinjection pump of the kind having one or more inlet or relief portswhich are so controlled by the pump plunger or b a separate valve as tobe opened during th the earlier and later portions of each plungerdelivery stroke to render these portions of the stroke inoperative sothat fuel is only forced through the delivery passage during anintermediate operative part of each delivery stroke.

let or relief port or ports in the cylin lln a liquid fuel injectionpump of the above kind according to the present invention, means areprovided for positively closing the delivery passage at the moment whenor immediately after the relief or inlet port is opened to terminate theoperative part of the delivery stroke. The inventionis particularlyapplicable to fuel injection pumps in which the pump piston acts both asa plunger and as the valve controlling the iner wall, and in this casethe delivery port is preferably also arranged in the cylinder wall andthe piston so formed as to close the delivery port positively as orimmediately after it opens the relief port to terminate the efiectiveportion of the delivery stroke.

In liquid fuel injection pumps wherein the pump plunger acts also as avalve, it is usual to provide a relief groove in the cylinder or pistonhaving a helical or like inclined edge so that by varying the relativerotational positions of the cylinder and piston the moment in theplunger delivery stroke at which the relief port is brought intocommunication with the pump pressure chamber can be varied so as to varythe quantity of fuel delivered. When the present invention is applied tosuch a construction, a delivery groove having acorresponding helical orlike inclined edge is conveniently provided in the cylinder or piston sothat when the moment of opening the relief port is varied, e. g. byrotating t e piston .relativel to the cylinder, the moment of closing oft e delivery passage is correspondingly varied whereby the closing ofthe delivery port at the moment of or immediately after the opening ofthe relief port to terminate the efiective portion of the deliverystroke is ensured whatever the relative rotational settings of thecylinder and piston.

The invention may be carried into practice 1n varlous ways but threealternative constructions according to this invention together with amodification of one of such constructions are illustrated by way ofexample in the accompanying drawing, in which Figure 1 is a sectionalside elevation of one construction,

Figure 2 is a sectional side elevation showing a modified form of pistonand cylinder which may be employed in the construction shown in Figure},

Figure 3 is a sectional side elevation of the operative part of thecylinder and piston of an alternative form of fuel pump according tothis invention, and

Figure 4: is a similar view to Figure 3 of the operative part of thepiston and cylinder of a still further construction of fuel pumpaccording to this invention,

In the construction shown in Figure 1 the fuel pump comprises a cylinderA containina piston B and having a delivery port C li a combined inletand relief port D in its circumferential wall. Mounted in ascrewthreaded 'bore in the lower end of the piston B is a bolt E onwhich acts the upper end of a tappet F mounted in a guide F and carryingat its lower end a roller F which engages a cam G on a camshaft G1 Acollar E surrounds the shank of the bolt and is acted upon by the lowerendof a compression spring E which serves to maintain the bolt E alwaysin contact with the tappet F and the roller F 2 in contact with thesurface of the cam G. The upper end of the' spring E bears upon anadjusting member H surrounding the lower end of the plunger -B andhaving a part H which is internally splined to engage correspondingexternal splines B on the plunger so that the plunger can reciprocateindependently of the member H but by rocking the member H by means of alever H thereon the rotational position of the plunger B relatively tothe cylinder A can be varied.

Formed in the circumferential wall of the plunger B adjacent to itsupper end is a helical relief groove B which communicates with thepressure chamber B of the pump through a passage B in the piston.

The arrangement is such that the plunger on the suction stroke draws infuel through the combined inlet and relief port D. During the initialpart of the delivery stroke of the plunger the port D is uncovered bythe piston, so that during this portion of the delivery stroke fuel isreturned to the inlet passage through the combined inlet and re liefport D. After the a certain distance on its delivery stroke it plungerhas moved covers the port I) so that flow of fuel through this port isstopped and fuel is forced through the passage B and groove B and thencethrough the delivery port C which during this period communicates withthe groove B Such delivery continues until the upper edge of the grooveB uncovers the port D and the arrangement is such that as or immediatelyafter the port D is uncovered by the upper edge of the groove B thelower edge of this groove closes the delivery port C so that at themoment when or immediately after communication is reestablished betweenthe pressure chamber of the pump and the relief port, communicationbetween this pressure chamber and the delivery port is cut off.

It will be seen that by rocking the plunger 18 by means of the lever Hthe length of the effective portion of the-delivery stroke during whichthe port D is closed, and hence the quantity of fuel injected, can bevaried but that at all rotational settings of the plunger the deliveryport C will be closed positively by the lower edge of the groove B atthe moment when or immediately after the Y relief port D is reopened toterminate the effective portion of the delivery stroke.

lln the construction shown in Figure 2 the arrangement is generallysimilar to that shown 1n Figure 1 except that the cylinder A is providedwith a port D which acts solely as an inlet port and has a separaterelief port D in addition to the delivery port C the arrangement beingsuch that some of the fuel drawn in through the inlet port D on thesuction stroke of the pump is forced out again during the initial andfinal stages of the delivery stroke through the relief port D lfn thisconstruction also, instead of the helical recess 18 in the pistoncommunicating with the pump pressure chamber B through a passage in thepiston, it communicates with the pressure chamber through a slot B inthe circumferential wall of this piston.

In the alternative construction illustrated in Figure 3, the pumpcomprises a cylinder J Within which reciprocates a piston K. Thecylinder is provided with a combined inlet and relief port L, a furtherrelief port M and a delivery port N, while the piston is provided with ahelical upper edge K and also with a circumferential groove K having ahelical upper edge. In order to reduce the quantity of fuel in thepressure chamberftl' the plunger is provided with a portion K of reduceddiameter which extends above the upper helical edge K as shown. Thegroove K communicates with the pressure chamber of the pump through apassage K in the plunger.

In this construction fuel is drawn in from the ports L and Mthrough thegroove K and passage K during the suction stroke and during the initialpart of the delivery stroke is forced-out through the combined inlet andrelief port L- When the lower edge of the groove K covers the port Lfuel is delivered from the pressure chamber of the pump through thedelivery passage N and this delivery continues until the upper .helicaledge of the groove K uncovers the relief port M. As or immediately afterthe relief port M is thus uncovered the helical edge K covers the de-.

livery port N so that this port is positively closed at or immediatelyafter the moment when the relief port M is opened to terminate delivery.

In this construction also, by rotating the plunger it will be seen thatthe length of the 'efiective portion of the delivery stroke of theplunger can be varied but that whatever the rotational position of theplunger the delivery port N will always be closed at or immediatelyafter the moment when the relief port M is opened to terminate theeffective portion of the delivery stroke.

In the construction shown in Figure 4 the pump comprises a cylinder 0within which reciprocates a piston 1 The cylinder is provided with twointernal circumferential grooves 0 0 the groove 0 having a lower helicaledge while the groove 0 has an upper helical edge. The groovecommunicates with a combined inlet and relief passage Q3 while thegroove communicates with a delivery passage R.

Formed in the piston P is a vertical passage P from which lead tworadial passages P P adapted to communicate respec tively with thegrooves 0 O in the cylinder during the desired portions of the pistonstroke.

With this construct on fuel is drawn in through the passage Q during thesuction stroke, the face of the piston lying below the upper edge of thegroove at the end of such suction stroke so that during the initial partof the delivery stroke fuel is forced from the pressure chamber of thepump back into the inlet passage Q. As soon as the upper face of thepiston P passes the upper edge of the groove fuel begins to be deliveredthrough the passages P and 1? into the groove 0 and thence through thedelivery passage R, and this delivery continues until the passage Pcomes into communication with the groove 0 At or immediately after themoment when the passage P? comes into communication with the groove 0the passage P passes the upper edge of the groove 0 so that the pressurechamber of the pump is substantially simultaneously cut off fromcommunication with the delivery passage R and brought into communicationwith the combined relief and inlet passage Q to terminate the effectiveportion of the plunger delivery stroke.

In this construction also by rotating the plunger P the length of theefiective portion of its delivery stroke can be varied but whatever itsrotational position the passage P will always be positively closed bythe upper edge of the groove 0 approximately at the moment when thepassage P comes into communication with the groove 0 to terminate thefuel delivery period.

It is to be understood that the constructions illustrated are given byway of example only and that the means for positively closing thedelivery passage at or immediately after the moment when the relief portis opened to terminate the efi'ective part of the delivery stroke may beseparate from the pump plunger and other details of construction may bevaried without departing from this invention; Further the invention maybe applied to fuel injection pumps in which a separate valve controllinginlet or relief ports is operated in timed relation to the piston torender inoperative the earlier and later portions of each plungerdelivery stroke.

1 What we claimas our invention and desire to secure by Letters Patentis 1. A. liquid fuel injection pump for internal combustionengines,including in combination a cylinder having a delivery passage, a reliefpassage and at least one relief 'port, a plunger adapted to reciprocatewithin the cylinder and act as a valve to open a relief port during thelater part of the suction stroke and beginning of each delivery strokeand having on the one hand a relief groove therein which uncovers arelief port during the later part of each delivery stroke so that fuelis only delivered through the delivery passage during an intermediateoperative part of each delivery stroke, and on the other hand a deliverygroove which communicates with the delivery passage during at least suchintermediate part .of the delivery stroke but has an'edge which coversthe delivery passage as the relief groove comes into communication withthe relief port, the edge on the relief groove which uncovers the reliefport and the edge on the delivery groove which covers the delivery, portat the end of the fuel delivery period being formed correspondinglyhelical, and. means for causing relative rotation between the pumpplunger and the cylinder whereby the quantity of fuel delivered on eachdelivery stroke can be varied while maintaining synchronism between theopening of the relief port and the closing of the delivery passage atthe end of the delivery period.

2. A liquid fuel injection pump for internal combustion enginesincluding in combination a cylinder having a fuel delivery passage andat least one relief port, a plunger adapted to reciprocate within thecylinder, means acting as a valve to open a relief port and maintain itopen during the end of the suction stroke and the beginning and end ofeach delivery stroke, whereby fuel is only delivered through thedelivery passage during an intermediate operative part of each deliverystroke, and means forpositively closing the fuel delivery passageagainst pressure within the pump pressure chamber as the relief passageis opened to terminate the delivery period.

3. A liquid fuel injection pump for internal combustion engines,including in combination a cylinder having a fuel delivery passage andat least one relief port, a plunger adapted to reciprocate within thecylinder and act as a valve to open a relief port and maintain it openduring the end of the suction stroke -and the beginning and end of eachdelivery stroke, whereby fuel is only delivered through the deliverypassage during an intermediate operative part of each delivery stroke,and means for positively closing the fuel delivery passage againstpressure within the pump pressure chamber as the re lief passage isopened to terminate the delivery period.

4. A liquid fuel injection pump for internal combustion engines,including in combination a cylinder having a fuel delivery passage andat least one relief port, a plunger adapted to reciprocate within thecylinder and having a part acting as a valve which not only maintainsopen a relief port during the later part of each suction stroke and thebeginning ,and end of each delivery stroke, whereby, fuel is onlydelivered through the delivery'passage during an intermediate operativepart of each delivery stroke, but also as a-valve for positivelyclosing'the' fuel delivery passage as the relief port is opened toterminate the delivery period. 1

5. A; liquid fuel injection pump for internal combustion enginesincluding in combination a cylinder having a fuel delivery passagev andat least one relief port, a plunger adapted to reciprocate within thecylinder, means acting as a valve and having controlling edges thereonwhich maintain open a relief port during the earlieran'd later parts ofeach delivery stroke, the controlling edge the quantity of fuel injectedby the pump on each delivery stroke While maintaining synchronismbetween the opening of the relief port and the closing of the'deliveryport at the end of the delivery-period.

In testimony whereof We have signed our.

names to this specifieation.

RONALD WHITEHAIR VIGERS. ERNEST EDWARD CHATTERTON.

